Microstructure and durability of low-clinker carbonated mortars containing metakaolin and brick powder

In this paper, the effect of the incorporation of metakaolin and brick powder on the durability properties of mortars was investigated. Mortars with a water-to-binder ratio of 0.5 and different substitutions of Portland cement by metakaolin (MK) and brick powder (BP) were tested. The experimental program covers compressive strength, natural and accelerated carbonation, capillary absorption, water porosimetry, water-vapor transmission permeability (WVTP), thermogravimetry analyses, and cracking tests. Results show that cement substitution by MK or BP improves the compressive strength of mortars, and the optimum content for achieving the best compressive strength is 25% for MK and 15% for BP. With regard to durability properties, the incorporation of MK and BP in mortars reduces their capillary absorption, total porosity, water-vapor transmission permeability, and resistance to carbonation. Noted that the mortar carbonation can considerably affect the durability properties, especially by an increase in the capillary absorption, total porosity, and WVTP.